1. Video conferencing
• Introduction
• Standards
• Products
• Internet telephony
• Computer Telephony Integration (CTI)
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2. Introduction
• Video conferencing can be used for
+ Audio-visual communication
+ Sharing of documents, tables, pictures, etc.
• Several benefits
+ Traveling costs
+ Response time
+ Better understanding (body language)
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3. Systems
• Two main types:
+ Video conferencing rooms
+ Video conferencing software
• Video conferencing rooms are for group meetings
+ Organization either has it own premises or rents them
from operator
• Video conferencing software is for personal use
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4. Equipment
Video/audio Modem, ISDN
capture or LAN
Communication
network
Audio
card
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5. Group Meetings
• Two types of video conferences:
+ Point-to-point conferences (video telephony)
+ Multipoint conferences (group meetings)
• In group meetings, there are two ways to share
turns (i.e., floor control):
+ Automatic selection (e.g., based on audio)
+ Chairman
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6. Multipoint Conferences
Communications
network
Multipoint server
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7. Standard Families
• Integrated Services Digital Network - ISDN
(H.320)
• Networks supporting QoS (H.310, H.321, and
H.322)
• Local area networks - LAN (H.323)
• Plain old telephone systems - POTS (H.324)
• Shared workspaces (T.120)
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8. Standard families (cont.)
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10. H.320
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11. Video
• Two resolutions:
+ Quarter Common Intermediate Format (QCIF): 176 x
144
+ Common Intermediate Format (CIF): 352 x 288
• Frame rates 7.5, 10, 15, or 30 frames per second
• Motion estimation can be used, but is not
necessary
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12. Audio codecs
• Three different audio codecs:
+ G.711 48-64 Kbps narrow band
+ G.722 48-64 Kbps wide band
+ G.728 16 Kbps narrow band
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13. Different classes
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14. H.324
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15. H.324
• Meant for Plain Old Telephone Systems (POTS)
• H.263 can be used for below 64 Kbps video
coding
+ sub-QCIF (128 x 96), QCIF (176 x 144), CIF (352 x
288), 4CIF (702 x 576), and 16CIF (1408 x 1152)
• G.723.1 audio codec transmits at 5.3 or 6.3 Kbps
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16. H.324 (cont.)
• Can use even 28.8 and 33.3 Kbps modems (V.34)
• Codecs are better, but quality is worse than H.320
+ H.320 has much more bandwidth than H.324
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17. H.323
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18. H.323
• LANs (Internet & Intranet) without QoS support
• Clients, multipoint servers, gateways and
gatekeepers
• Real-time transport protocol (RTP)
• New audio codec G.729 (8 Kbps)
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19. Gateway
• The gateway allows the integration of H.323
networks with other networks
• Tasks:
+ transformations between media formats
+ transformations between communication protocols
+ transformations between audio and video codecs
+ connection setup and tear-down
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21. Gatekeeper
• Gatekeeper takes care of resource reservations
• The amount of simultaneous users can be limited
• Transforms connection requests from outside to
internal addresses and vice versa
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22. Multipoint Server
• Required when three or more clients participate
the conference
• Is composed of two parts:
+ Multipoint Controller takes care of connections
+ Multipoint Processor(s) transform(s) media streams
• Processors can also combine streams:
+ Mixing
+ Switching
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23. Multipoint Server (cont.)
• Videoconferences can be set up in three different
ways:
+ unicast, multicast, and broadcast
• Three ways of practical implementation:
+ centralized, distributed, and hybrid
• In practice H.323 is implemented on top of IP etc.
protocols
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24. Different alternatives
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25. Protocol stack
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26. T.120
• Implements the extra services:
+ conformance
+ image transfer
+ shared workspaces
+ file transfer
+ multipoint conferences
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27. T.120 (cont.)
• T.120 is composed of three layers:
+ transport layer
+ protocol layer
+ application layer
• Transport layer is divided into three levels:
+ transport protocol
+ multipoint conference
+ conference control
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28. Transport layer
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29. T.120 (cont.)
• Protocol layer is composed of
+ image transfer (T.126)
+ binary file transfer (T.127)
+ share application transfer (T.Share)
+ resource reservation (T.RES)
• New standard family T.130 is under development
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30. Products
• Video conference bridges
• Video networks
• Video conference rooms
• Workstations
• Gatekeepers
• Gateways
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31. Video conference bridges
• Support primarily H.320 and T.120 standard
families
• Allow multipoint video conferencing
• Support few tens of users
• Participants either call to the bridge or the bridge
setups the connections itself
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32. Video networks
• Best possible image quality
• Intended primarily for conferences
• Uses either ISDN or ATM network
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33. Video conference rooms
• Intended for video conferencing
• Maintained by companies or operators
• Based on H.320 (ISDN) standard family
• H.323 (Internet) standard family is coming
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34. Workstations
• LAN, ISDN, or modem card
• Audio and video cards
• Software (e.g., Microsoft Netmeeting, Picturetel,
Intel)
• H.320 most common, but H.323 is coming (client
software is available)
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35. Gatekeepers
• Required by H.323 standard family
• For example, Intel LANDesk Conferencing
Manager
+ automatic gate keeper
+ zone management
+ outbound route management
+ incoming call routing
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36. Gateways
• Intel LiveGateway
+ bi-directional connection between H.323 and H.320
systems
+ format transform between H.323 and H.320 systems
+ supports also H.320 multipoint server
+ four gates in on PC
+ either local or gate keeper based administration
• Both Intel LANDesk Conferencing and
LiveGateway are Windows NT based
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37. Internet telephony
• With suitable hardware and software computers
connected to Internet can be used for telephony
• No extra charges, but the quality is not very good
• Gateways to ordinary telephone network also
available
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38. Internet telephony (cont.)
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39. Internet telephony (cont.)
• Some long distance operators use Internet
connections for telephony
• Allows the use of compression
• For example, 64 Kbps -> 2.4 Kbps
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40. Calls within organization
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41. Public Internet calls
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42. Internet telephony products
• Microsoft Netmeeting supports H.323 and T.120
standard families
• Includes H.263 video codec
• Compatible with Intel and PictureTel products
• Utilizes Intel Pentium MMX technology
• Other products include White Pine Software CU-
SeeMe, IBM Internet Connection Phone, VDOnet
VDOPhone
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43. CTI
• Computer Telephony Integration (CTI) integrated
computers and telephones
• Brings savings and increases efficiency (invest
return time usually under year)
• Several different implementations
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44. CTI block diagram
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45. CTI applications
• Voice mail (answering service)
• Automatic call transfer
• Intelligent call routing and distribution (call
centers)
• Voice text (timetable, etc.)
• Fax requests (information delivered via fax)
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46. CTI applications (cont.)
• Interactive telephone services (reservations,
orders, etc.)
• Call records (automatic recognition of customers)
• Gateways (video conference with standard
telephone)
• Call management (automatic dialing)
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47. CTI implementations
• CTI can be based on separate server
• Another alternative is to join telephone directly to
workstation
• Video conference, Internet telephony, and CTI
systems can be integrated
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48. Call Center
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49. Integrated system
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50. CTI standards
• Multi-Vendor Integration Protocol (MVIP)
• System Computing System Architecture (SCSA)
• Both are buses connecting different PC cards
• Buses are used for call traffic within PC
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51. PC cards
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52. CTI APIs
• Microsoft Telephony Application Programming
Interface = TAPI (-93)
+ Windows applications
• Novell Telephony Service API = TSAPI (-93)
+ Novell servers
• IBM CTI API
+ Switches and their interfaces
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53. CTI APIs (cont.)
• SCSA framework
• Sun Java Telephony API = JTAPI
+ Java-framework
+ utilizes above mentioned API definitions
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